The invention relates to a karabiner comprising a fixed C-shaped body having a first end shaped as a securing part and a second end for articulation of a gate movable around a pivoting spindle between a closed position and an open position, said gate comprising:                a latching part situated opposite the pivoting spindle to operate in conjunction with the securing part in the closed position,        a return spring to return the gate to the closed position,        a locking ring fitted coaxially around the gate and having a shorter length than that of the gate, said ring being movable between a first locked position blocking the gate in the closed position and a second unlocked position enabling the gate to be moved to the open position,        and a lock-bolt able to block the ring positively in said first locked position.        